The patient’s chest tube is not inserted far enough. It is also a bit high residing between ribs 3-4.

Chest tubes have a side port and a distal port for suctioning fluids, air from the pleural space. There is a radiopaque line seen on the tube that is interrupted at the side port (see magnified image). In this case the radiograph shows that the side port is subcutaneous and not inserted all the way into the pleural space. The chest tube needs to be replaced!

On an upright CXR, a pneumothorax is one of the more easily identifiable pathologies in the thoracic cavity. The presence of air separates the parietal pleura and visceral pleura, resulting in the lung tissue being pushed towards midline. This results in the edge of the lung tissue being easily identifiable (purple arrows). The rest of the cavity is devoid of lung markings.

It is important to note that the size of a pneumothorax can vary greatly. Therefore even if the absence of lung markings isn’t as striking as it is in this picture, the edges of the thoracic cavity should always be closely examined to see if there is any evidence of air. On the other extreme is a tension pneumothorax, which is defined as an expanding pocket of air in the thoracic cavity, which causes half of the lung to completely collapse and shift the mediastinal structures in the contralateral direction.

Pneumoperitoneum: air in the abdominal cavity

The presence of air in the abdominal cavity comes from two major sources: outside the body or the GI tract. Air from outside the body enters into the abdominal cavity through either iatrogenic (surgery, peritoneal dialysis) or traumatic (penetrating wound) routes. Air from the GI tract enters if any segment of the bowel is perforated (most commonly secondary to a duodenal ulcer). On an upright CXR, as is shown above, the air rises to the level of the diaphragm and can be identified.

Even though the subdiaphragmatic air in this picture is clearly evident, CXR’s are not the gold standard diagnostic test for pneumoperitoneum. Abdominal CT scans can pick up much smaller amounts of air that may be difficult to visualize on a plain film.

Subcutaneous Emphysema: air in subcutaneous tissue planes

The image above has distinct areas of radiolucency in the supraclavicular area as a result of air tracking in the subcutaneous tissue, which is defined as subcutaneous emphysema. The area is patchy from the infiltration of air into soft tissues.

Similarly to pneumomediastinum, the air comes from either inside the body (secondary to pneumothorax, pneumomediastinum) or outside the body (penetrating trauma, chest tube insertion site). The air travels along fascial planes between the dermal and muscular layers. Another, more serious, cause is necrotizing fasciitis. In this case, however, it is likely that the air entered into the subcutaneous tissues as a result of trauma, which also resulted in a pneumothorax.

One finding on this Xray is very concerning. The Xray showed free air under the diaphragm.

A further diagnostic study was obtained (CT abdomen/pelvis):

Turns out this patient has pneumatosis cystoides intestinalis. He has a history of this disorder and has had a prior laparoscopy showing multiple cystic structures in the intestinal walls.

Findings on imaging:

1. Chest Xray: Concern for free air underneath the diaphragm. He also has a tracheostomy, pacemaker, scoliosis, and a right lower lung infiltrate.

2. CT abdomen/pelvis: The coronal imaging shows multiple cystic structures full of free air in the cecal area. The cross-sectional imaging above shows a large amount of pneumoperitoneum.

Luckily this patient has a history of pneumatosis cystoides intestinalis. He has had multiple abdominal CT’s showing similar findings. Clinically he had no abdominal tenderness. Keep this rare diagnosis in mind for the patient presenting with free air in the abdomen! Information about pneumatosis cystoides intestinalis:

Cavitary lesions in the lungs are gas or fluid filled compartments in an area of pathology, such as a consolidation or a mass. Interestingly, a specific set of pathologies are known to cause this specific finding. Cavitary lesions can be detected on a chest x-ray, as is shown below.

The lesion practically jumps out of the picture on the AP view, but the colored circles are there just to point out the entire area of pathology (blue) and the cavity within (red). The pathology is a bit harder to see on lateral view, but the cavity has an air-fluid level that is easily identified as a vertical line separating a lighter fluid filled portion from an air filled portion. This air-fluid interface is often called a meniscus. You might remember being in chemistry class and measuring water out of tall beakers where the water stuck to the sides of the glass creating a concave meniscus. The surface tension of water allows it to stick to both itself and surrounding surfaces. If you look close enough, you’ll notice that the air-fluid level in the image above, best visualized in the AP view, has a slightly concave shape because the liquid at the bottom is sticking to the solid sides of the cavity.

The underlying pathophysiology is an interesting concept to understand when discussing cavitary lesions. A cavity can form in lung tissue for various reasons, but infection is the major underlying cause. Abscesses are localized collections of pathogens, fluid and immune system components that are walled off from the surrounding tissue, therefore creating a fluid-filled cavity. Tuberculosis is a disease process that involves caseous necrosis, which results in coagulation of cell proteins and liquefaction of cellular components. Eventually, the liquid portion drains out through the lymph system or through the bronchi, leaving air pockets behind. Necrotizing pneumonia and non-infectious processes such as ischemia and neoplasm can also cause a similar picture. Rheumatologic diseases such as granulomatosis with polyangitis and sarcoidosis also cause cavitary lesions by causing localized inflammation, which in turn leads to an area of increased mass, which then in turn can cavitate once the inflammatory reaction recruits fluid to the area. In other words, most of these processes, even if they aren’t inherently related to one another, all converge on the same mechanism of causing a localized area of inflammation.

With such a wide array of categories to choose from, it is perhaps more important than usual to contextualize the radiographic image with information about the patient.

This particular patient is a 30 year old male who presents with a cough. He has been traveling around the world to multiple continents including Sub-Saharan Africa. The extensive travel history, including to continents with rare infectious diseases leaves infection at the top of the differential. Things like Staphylococcal pneumonia, fungal infections and even amebiasis are possible because of the patient’s travel history. For a complete list of the infectious causes of a cavitary lesion, check the first two references at the bottom of the page.

How many times have you had trouble with figuring out what type of cardiac device (e.g. pacemaker/defibrillator) a patient has implanted? A patient presented to our ED with chest pain, palpitations. He did not have his device card with them, no prior visits to our ED, and did not know the manufacturer of the device. How do you decide which company to call for interrogation?

Here is an article I found with radiologic characteristics of devices that can help identify which company produced the device. It has a great identification algorithm they coined the CaRDIA-X algorithm:

There are 5 major manufacturers currently: Medtronic, Boston Scientific, St. Jude, Biotronik, and Sorin Group. Each device manufactured by these companies have certain differentiating characteristics of can shape, battery shape, alphanumeric codes, capacitor shadows, coil types, etc. Turns out you can identify the manufacturer using the device characteristics on chest X-ray relatively easily.

In the case I was describing above the patient had an easily identifiable Medtronic device and we were able to get it interrogated. Our ED now has the algorithm posted at our doctor’s station so we can utilize it for device identification.

Pt is a 52 y/o man with a history of smoking, atrial fibrillation, and HTN that presents to the ED today with a 2-3 day history of fatigue, weakness, fever, generalized body pains, drenching night sweats, increased urinary frequency, L ear discomfort, throat discomfort and blurry vision in the morning. The symptoms came on suddenly and have been constant since the beginning of the episode. The fatigue and weakness cause the patient to want to “drop into a hole” and sleep. His nightly sleep patterns have been disrupted by his night sweats and his increased urinary frequency. The night sweats are drenching and he often wakes up in the middle of the night with his shirt completely soaked. Around 8-9 AM in the morning he reports being cold and getting chills. He also has some lower sternal chest pain that occurs mostly with deep breathing. The pain does not radiate. The pt has a 30-35 year history of smoking cigarettes and drinking 15-20 alcoholic drinks/week. The pt stopped smoking yesterday with the intent to quit.

The pt has no change in appetite or weight, no new masses or lumps anywhere on his body and no syncope or LOC. The pt denies any history of similar symptoms. The pt denies any family history of these symptoms. The pt denies any sick contacts. The pt’s wife does not have similar symptoms. The patient has no N/V or history of recent travel. The pt was routinely tested for tuberculosis 2 years ago as part of an employment physical and the test was negative.

With all of that in mind, let’s take a look at the x-ray again. The last post went through the ABCDE methodology to review the image and the A through D aspect was pretty well outlined there. The airway is patent, there is no obstruction and it lines up with the cervical spinous processes. The bones have no step-offs or other evidence of fractures and there are 10 ribs visible. The cardiac silhouette is not enlarged (in other words, not more than twice the width of the chest cavity) and the AP window sits between the aortic arch and pulmonary artery. The diaphragm has normal contour and the costo-vertebral angle is sharp.

The E is where things get interesting. One of the ways I like to do it is to try and look for asymmetry in the lung fields. And I think I see something!

The blue circle seems like a focal area of consolidation (either liquid or solid). That same “opacity” is not present on the corresponding place on the L lung field. I think its important to note that this finding has a large differential diagnosis attached to it, even if you put the finding on the x-ray in context with the case presentation. Most of the diagnoses on the list would be infectious, like TB or pneumonia, but other possibilities include lung cancer, edema, hemorrhage and systemic inflammatory conditions like sarcoidosis.

The radiologist read that image as most likely a case of lobar pneumonia. There was some hedging by the radiologist on the read because the lateral film was taken from L to R, therefore the opacity in the R lung field was very hard to see (that’s why I didn’t include a lateral view as well, but we can save that particular x-ray type for another post). In general, you want to get two views on any pathology on x-ray because it’s important to try and construct a 3D image in your head about where the pathology is located.

In any case, his patient presented with fever, cough, loss of energy, chills and body aches, with all of those symptoms having an acute onset. This makes an infectious process more likely (I say “more likely” because as everyone in medicine learns at some point or another, it is very dangerous to talk and think in absolutes). He was treated empirically with antibiotics for pneumonia.

Hopefully this example helps you to have a system in place when you look at any chest x-ray. If you have any questions, feel free to drop them in the comments and I’ll do my best to answer them. Also, if you have any requests for certain types of images you would like to see for the next post, also let me know in the comments. Until next time!

In these “Student Corner” pieces, we will go over certain aspects of radiology in EM that are of interest to medical students. Topics will include: common (and interesting) case presentations with accompanying imaging, schematics for how to read different types of imaging in various anatomical locations, discussions on what types of imaging to order and when in the EM setting, and others.

In this inaugural edition of the Student Corner, we’ll take a look at how to tackle reading an anterior-posterior chest x-ray.

For starters, it is important to understand that having a “gameplan” for reading any type of image is key when you first start out trying to decipher radiological images. As a reader and interpreter, you must be systematic in your thought process as you analyze the image in front of you. For chest x-rays, there is a classic schematic: ABCDE. Any medical student will tell you that this is not the only time you will see “ABC…” used as a way to quickly memorize something, but at least it’s easy to remember.

Here’s the image we are going to use and let’s start to dissect it using the mnemonic:

Note: For the purpose of keeping this a short piece, we’ll only focus on the anterior-posterior view only.

The upper airway, including the trachea, carina and both main bronchi, should all be visible on an AP view. Things to look for include deviation of the trachea away from the midline (there is some deviation to the patient’s right in this image, but this is due to the aortic arch, which passes to the left of the trachea as it passes posteriorly in the mediastinum), obstruction due to aspiration of a foreign object and obscuring of the upper airway due to enlarged mediastinal lymph nodes.

Let’s explore tracheal deviation a bit further. Deviation from the midline is not associated with a defect in the trachea itself, but with a force from either the R or L side of the chest cavity that is pulling or pushing the trachea to one side or the other. For example, introduction of air into one side of the chest cavity will cause that lung to collapse due to the loss of negative intrapleural pressure. The collapsed lung will shrink to the size of a ball and “push” the trachea to the opposite side. You can think of the two lungs like bungee cords that put roughly equal force on the trachea in each direction. If one of the cords snaps or is released from where it is attached to, the cord that is still intact will pull the trachea towards one side, resulting in a deviation that will show up on a CXR.

A CXR offers a good view to look for rib fractures and clavicle fractures. Clavicular fractures are usually easy to spot, as they usually reveal distinct fracture lines in the middle 3rd of the clavicle. Hairline fractures are less common. Rib fractures are sometimes hard to spot, but each rib should be followed across it’s length to look for fracture lines or step-offs (disruptions in the normal curve of the rib) that could indicate a fracture.

The number of ribs is also important to assess because it is an indirect measurement of the volume of the chest cavity. Hyperinflated lungs are usually the result of obstructive disease where the patient is unable to fully expel the air that is inhaled with every breath they take–this increase in residual volume will build up over time and overinflate the chest cavity. This overinflation will result in a greater-than-normal number of ribs being visible on an AP view. Normally, you should expect to see 8-10 ribs on an upright chest X-ray, depending on whether the patient was instructed to exhale or inhale before the picture was taken.

C-Cardiac

Legend: Red Dashed Lines–heart borders

This part of the mnemonic involves the heart and surrounding structures. The silhouette of the heart should be identified and the heart borders should be clear. A general rule of thumb is that the heart base should not be wider than 1/2 the total width of the diaphragm. As with a lot of “general rule of thumb”s in medicine, it’s not quite clear whether this has any diagnostic value–for example, if the heart base is indeed 1/2 the width of the diaphragm on CXR, is that really sensitive for cardiomegaly? In any case, it’s something to keep in mind.

The aortic arch and the L pulmonary artery should be visible as two semi-circles above the left atrium. There is a space called the “AP Window” that has the following borders: ascending aortic arch (anterior), descending aortic arch (posterior), L pulmonary artery (inferior), inferior border of aortic arch (superior). The window should be “concave” in the sense that the lateral border should be caved in medially. If it is not, things like mediastinal lymphadenopathy and aorta/pulmonary artery aneurysms are possible.

D-Diaphragm

Legend: Blue Arrow–gastric air bubble; Red Arrow–costophrenic angle

The diaphragm has 3 major characteristics which you look for on CXR. One is the gastric air bubble, which allows you to identify that the stomach is on the left (as opposed to the right, as in situs inversus). Another is the contour of the diaphragm, which should be a “dome” shape. The right side should be a little higher than the left, thanks to the liver. The third is perhaps the most important: the costophrenic angle. It is the lateral point of attachment for the diaphragm and it should be a sharp, triangle-shaped region at either end. The angle should be acute. If the angle is closer to 90 degrees, then one possible explanation is that the lungs are hyperexpanded (perhaps because of COPD) and pushing the diaphragm down into the abdomen. “blunting” of the angle refers to a radio-opaque marking of the angle that usually is indicative of pleural effusion.

E-Everything Else

Everything else is…everything else. Mostly this means the lung parenchyma itself. For this, asymmetry is key. Compare left and right and see whether there is a difference. More on this particular section of the read later.

—–

Now you should try to read the above x-ray for yourself and type your own version of the read in the comments if you’d like. If not the entire read, then try to identify the pathology in the x-ray and post your answer in the comments. Any questions/comments would also be appreciated.